Depends.
There has been a long discussion
here on how the continuously of residence gets counted. So depending when the non-EEA national travel abroad, some of the absences could get counted for one year of residence while the other absences might be counted for the following year so in total he/she will not be more than 6 months abroad in a single year.
Also if he/she goes abroad and returns, then until the 6 months abroad have passed, he/she can use the EEA2 Residence Card without any problems.
As I wrote, in practice, It is very unlikely he/she will have any problems entering the UK even if he/she spent more than 6 months abroad in a given year.